A bank in an organic light emitting device (OLED) serves to specify a shape of a pixel by forming a polyimide insulation layer in every other area except for a region in which an organic light emitting material will be deposited and act as the pixel, and allows each pixel to be electrically independently driven. As a material for forming the bank, a positive type photosensitive polyimide (PSPI) is frequently used.
The existing polyimide-based transparent bank has a limitation in preventing reflection by external light, and defects occurred in terms of image quality, such as occurrence of light leakage due to reflection by metal electrode. Further, when a polarizing plate is used in order to alleviate these problems such as an external light reflection, a transmittance is significantly reduced, and as a result, high voltage driving is required in order to obtain a higher transmittance, and accordingly, there occurs a problem in that the lifetime of the organic light emitting device is shortened for this reason.
Therefore, there is a need for studies on a material for improving visibility by alleviating an external light reflection problem in an organic light emitting device in the art.